Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$147.62	6.781%	$157.6301	$157.63	$157.65	$157.60
Purchase #2	$109.94	6.796%	$117.4115	$117.41	$117.40	$117.40
Purchase #3	$242.30	13.702%	$275.4999	$275.50	$275.50	$275.50
Purchase #4	$96.80	7.772%	$104.3233	$104.32	$104.30	$104.30
Purchase #5	$83.98	6.481%	$89.4227	$89.42	$89.40	$89.40
Purchase #6	$35.98	6.410%	$38.2863	$38.29	$38.30	$38.30
Purchase #7	$222.65	9.667%	$244.1736	$244.17	$244.15	$244.20
7 purchase totals =	$939.27		$1,026.7474	$1,026.74	$1,026.70	$1,026.70